1. Field of the Invention
This invention relates to top drive well drilling and operation apparatus and tubular handling apparatus related thereto.
2. Description of the Prior Art
It has previously been common in well drilling and other well operations to impart motive force to the drill string or other tubular members being worked with by means of the old rotary table drive apparatus or electric motor top drives. The old rotary drive tables are inefficient and costly. The electric top drives have had numerous problems; for example, to move and support drill strings weighing up to 500 tons, the Direct Current traction motors used in electric top drives must be very large, consequently they require a large and effective motor cooling system. Also all of the safety problems associated with electricity are considerations when using an electric top drive. Because of these shortcomings, obtaining compliance with accepted safety codes and insurance certification for the use of electric top drives has been a tedious, expensive, and time-consuming process. There are also numerous structural/functional disadvantages associated with the use of electric top drives; for example, one prior art electric top drive utilizes an expensive thrust bearing to support the drill string rather than using the shaft of the motor itself. Another prior art electric top drive has an electric motor which is offset from the shaft supporting the drill string which results in an imbalance in the distribution of the reactive torque applied.